2. Of all things which move, some have the cause of their motion within themselves, others receive it from without: and all those things only are moved from without which are without life, as stones, and pieces of wood, and whatever things are of such a nature as to be held together by the constitution of their matter alone, or of their bodily substance. That view must indeed be dismissed which would regard the dissolution of bodies by corruption as motion, for it has no bearing upon our present purpose. Others, again, have the cause of motion in themselves, as animals, or trees, and all things which are held together by natural life or soul; among which some think ought to be classed the veins of metals. Fire, also, is supposed to be the cause of its own motion, and perhaps also springs of water. And of those things which have the causes of their motion in themselves, some are said to be moved out of themselves, others by themselves. And they so distinguish them, because those things are moved out of themselves which are alive indeed, but have no soul; whereas those things which have a soul are moved by themselves, when a phantasy, i.e., a desire or incitement, is presented to them, which excites them to move towards something. Finally, in certain things endowed with a soul, there is such a phantasy, i.e., a will or feeling, as by a kind of natural instinct calls them forth, and arouses them to orderly and regular motion; as we see to be the case with spiders, which are stirred up in a most orderly manner by a phantasy, i.e., a sort of wish and desire for weaving, to undertake the production of a web, some natural movement undoubtedly calling forth the effort to work of this kind. Nor is this very insect found to possess any other feeling than the natural desire of weaving; as in like manner bees also exhibit a desire to form honeycombs, and to collect, as they say, aerial honey.